Docker has changed how we develop software, especially when it comes to breaking it into smaller parts called microservices. When we use Docker, we run various programs on one computer. Sometimes, we need to make sure we’re using our storage space wisely. So, in this blog post, let’s explore the best practices of managing docker host disk space effectively.

Why Manage Docker Disk Space

It’s important to keep an eye on how much space your computer’s storage has. If it gets completely full (100%), it can cause problems for all the programs or services running on your computer. When you get a warning about low disk space, whether from a monitoring system or by checking manually, it’s crucial to take action promptly.

How to Check Docker Host Disk Space

To find out how much space your computer has left, you can use a command in Linux called “df -h“.

This will show you a list of your storage usage. It’s important to note that you should keep an eye on it, and if it goes above 95%, it could cause issues for your running programs or Docker containers, as we mentioned earlier.

Common Causes of Docker Host Filling Up

1. Unused Containers: Containers that are not being used anymore but still occupy space.

2. Container Logs: Regular logging activities can fill up the storage over time.

3. Dangling Images and Volumes: Images and Volumes that are not linked to any active container and accumulate over time.

4. Unused Images: Images that were used before but are no longer necessary. They can take up space even if not actively used. 

The Best Practices to Manage Disk Space Effectively

Alright, it’s time to see what can be done in such scenarios.

Method 1: Remove All Unused Images And Volumes

To manage disk space effectively, one recommended practice is to regularly remove unused images and volumes from Docker hosts.

This can be achieved using the command `docker system prune -a –volumes`, which performs a thorough cleanup by removing all unused images (both dangling and unreferenced), stopped containers, and volumes not in use by any containers.

However, caution should be exercised to ensure that no essential data resides in stopped containers that are no longer needed before executing this command.

Method 2: Remove Dangling Images from Docker Host

Another effective approach is to clean up dangling (untagged or unreferenced) images by utilizing the following Docker command:

docker rmi $(docker images --filter "dangling=true" -q --no-trunc)

Method 3: Setup Cron to Clear (Automation)

This command efficiently removes all dangling images from the Docker host, contributing to effective disk space management.

We can set up system cron to do this periodically.

Then simply add the cron on required time, recommended to run at off-peak.

This will clear docker disk space automatically.

Conclusion

To ensure optimal disk space usage and avoid unexpected issues, it is imperative to regularly implement cleanup and optimization practices on Docker hosts. This proactive approach, involving the removal of unused images and volumes, contributes to a more efficient and stable environment for running containers and applications.